These studies are aimed at understanding how the human immune system recognizes and destroys foreign cells. Special emphasis is placed on early antigen nonspecific cytotoxic responses (spontaneous cytotoxicity), which precede specific immune recognition. Both cell mediated and humoral mediated forms of spontaneous cytotoxicity have been examined. A different project has used the in vitro addition of both simple carbohydrates and defined anti DRw specific antisera disect cellular control phenomena. These studies have demonstrated a profound negative regulatory effect by both anti DRw antisera and simple carbohydrates.